Answer: c
Explanation: Grade 43 OPC has higher strength than grade 33 and lower than grade 53. Grade 33 used for finishing works under normal condition. Grade 53 is used for high rise building.

4. After how many days is strength of cement is tested and graded according to the result?
a) 7 days
b) 28 days
c) 1 day
d) 14 daysView Answer

Answer: b
Explanation: Cement blocks are prepared to test their compressive strength. With proper curing and attaining strength, these can be tested. It requires 28 days to fully cure and attain strength of required grade, say 43 N/mm2 for grade 43 OPC.

Answer: a
Explanation: Cement blocks can be tested at 1 day, 3 days, 7 days and 28 days. Usually 1 day doesn’t give any result. Strength of 43 grade OPC at the end of 3 days is 23, 7 days is 33 and 28 days is 43. So, it increases with time.

6. Grade 43 OPC shall be rejected if it remains in bulk storage in factory for:
a) More than 3 months
b) More than 1 month
c) More than 6 months
d) More than 4 monthsView Answer

Answer: c
Explanation: Cement stored in factory of more than 6 months has to be retested and rejected if it does not meet requirements. Time period of more than 3 months is for cement bags with vendors.

Answer: a
Explanation: The value is in accordance with the IS code 12269 for 53 grade OPC. Table 3 gives physical requirements and fineness is one of them.

9. Which of the following cannot be added in 33 grade OPC after burning stage?
a) Gypsum
b) Water
c) Colouring Agents
d) ClayView Answer

Answer: d
Explanation: The details and specifications regarding manufacture of 33 grade OPC is mentioned in IS 269. It says that after burning, only certain element like gypsum, water, performance enhancers, colouring agent can be added. More raw material-clay cannot be added.